水库水体近红外反射峰与叶绿素含量之间的关系初探     

杨敏  商少凌  汪文琦  林供  王郝京 《湖泊科学》2009,21(2):228-233

2007年8月至2008年9月,对厦门两个淡水水体(芙蓉湖、厦大水库)的叶绿素浓度和遥感反射率(Rrs)进行了连续观测.在叶绿素浓度6-322mg/m3的范围,Rrs光谱出现显著的近红外反射峰,中心位置在700-710nm之间,较之通常的荧光峰中心(683nm)向长波方向偏离.该峰在厦大水库始终出现在700nm,但在芙蓉湖存在时间变化,随着叶绿素浓度的增加,由705红移到710nm.由此,仿MODIS荧光高度(FLH)的定义,定义该峰的高度(简写为REH),对于水库和美蓉湖中心波段分别确定为700和710nm.REH与叶绿素浓度呈现显著相关,美蓉湖REH=0.0161g(chl)-7.8×10-6(R2=0.79,n=41),水库REH=0.0001chl+0.0002(R2=0.74,n=32).可见对十高散射的淡水藻华水体,可以并且需要通过改进FLH的波段选择,基于更长波段处的近红外峰的高度探测叶绿素浓度.  相似文献   

A holistic computational model for prediction of clay suspension structure     

Yuan Guo  Xiong Yu 《国际泥沙研究》2019,34(4):345-354

The formation of clay suspensions involves complex interactions among clay particles subjected to the geochemical environment during the sedimentation process. The structural characteristics have a major influence on the physical and mechanical behavior of the suspension. A modeling framework involving a Discrete Element Method (DEM) model with customized particle mechanical interactions is proposed in this paper for the holistic prediction of the physical structure of clay suspensions. The particle interaction force model is based on the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory that accounts for electrostatic repulsion, van der Waals attraction, contact repulsion, etc. Kaolinite is used as the model clay to demonstrate the model performance. The surface charge density of kaolinite is obtained through Atomic Force Microscope (AFM) force measurement and is implemented in the particle interaction force model in the subsequent simulations. Influencing factors, such as centrifugal acceleration, ionic concentration, platy structure of particles, and particle size, on the formation of kaolinite suspensions are studied with the numerical model and compare favorably well with the experimental data. This work lays down a unique framework consisting of computational modeling and microscale characterization of clay particles to holistically predict the characteristics of clay suspensions, which paves the basis to model and predict their bulk physical and mechanical behavior.  相似文献   

Clay minerals in the late Quaternary sediment of Tulare Lake,California: Implications for climate change,weathering, and erosion processes     

Junhua Guo  Christine Pyles  William Krugh  Rob Negrini 《国际泥沙研究》2019,34(5):432-443

The clay mineralogy of Tulare Lake sediment was examined to investigate hydroclimatic and environmental changes in the southern Sierra Nevada Mountains (SNM) since the most recent glacial maximum. Evolution of clay mineral assemblages elucidates significant changes in weathering, erosion, and hydroclimatic condition in the catchment. During the last glacial period (24.4–15.1 cal ka BP), low illite content implies less physical erosion of the granitic batholith rocks and a cold and arid environment in the southern SNM. Abrupt increases of illite content at 21.8–20.8 and 17.6 cal ka BP resulted from the glacier advances to the ablation zone and illite-rich glacier flour was transported down to the lake. The gradual increase of smectite induced by progressive depletion of illite-rich glacier flour from 17.6 cal ka BP toward the end of this period indicates climate was beginning to get warm and wet. From 11.9 to 5.3 cal ka BP, two warm and wet periods (10.7–9.4 and 8.2–5.2 cal ka BP) were characterized by high smectite/illite content ratios and low illite crystallinity values, suggesting intensive rainfall precipitation and more physical erosion in the highland and lowland catchment as well as more smectite formation in the terrace soils. Since the last glacial period, physical erosion, in comparison to the chemical weathering, was the dominant process responding to the hydroclimatic change in the Tulare Lake catchment. Moderate to weak chemical weathering was signified by the mostly low illite chemical weathering index of the core sediments. Such results suggest that vegetation cover in the southern SNM was low and limited.  相似文献   

双组份裂缝岩石非线性有效应力模型研究          下载免费PDF全文

肖文联  任席瑶  赵金洲  李闽  郑玲丽  杨玉斌 《地球物理学报》2018,61(12):5034-5043

为认识黏土矿物和裂缝对岩石有效应力的影响,提出了双组份裂缝岩石椭圆模型.同时,将双组份裂缝岩石椭圆模型等效为共聚焦的椭圆岩石环与椭圆黏土环的叠加;基于复变函数和保角变换,分别得到了黏土环内椭圆长半轴和短半轴与压力间的关系式.进而结合椭圆孔渗透率计算式和岩石有效应力表达式,计算与分析了岩石孔隙度、黏土矿物含量、硬度比以及椭圆孔截面纵横比等参数对有效应力系数的影响.结果表明,当岩石中不含黏土矿物时,有效应力系数随纵横比的减小而增大,且小于1.0,这与Bernabé的观点一致.当岩石中含有易于压缩的黏土矿物,且纵横比为1.0（孔隙截面为圆形）时,有效应力系数随硬度比和黏土矿物含量的增大而增大,甚至远大于1.0,这与Al-Wardy等的研究结论一致;当纵横比小于1.0时,有效应力系数表现出了明显的非线性特征,随硬度比的增大而增大——甚至远大于1.0,而随黏土矿物含量的增大而减小,纵横比对有效应力系数的影响受黏土矿物含量大小的影响.易于压缩组分和裂缝的存在使得岩石有效应力系数变化特征更为复杂.  相似文献   

盐相关盆地油气地质特征及其勘探认识——以红海盆地为例          下载免费PDF全文

张勇刚  吕福亮  范国章  王彬  李丽  李东  邵大力  杨姣 《盐湖研究》2012,20(1):9-15

全球已发现的工业油气田中与盐系地层有关的约为58%,总结盐相关盆地油气地质特征及其勘探经验,为含盐盆地的油气发现具有非常重要的意义。通过对红海盆地的岩盐发育和分布规律研究、盆地生储盖特征分析及红海盆地实际勘探经验总结,认为含盐盆地具有以下特征:含盐盆地盐系地层发育,岩盐因构造变形可形成多种类型的盐构造,油气勘探应以寻找各种盐构造油气藏为主;含盐盆地盐下易形成高温高压,盐下储层主要为碳酸盐岩和砂岩,这种异常高压对储集层的储集性能是有利的,盐下应以储层类型和圈闭识别为主要勘探目标;含盐盆地地质情况复杂,勘探工程难度大,需加强钻井工程研究;含盐盆地盐下地震成像普遍较差,加强盐下地震处理技术研究,辨别盐下"假构造",是盐盆勘探取得突破的关键。  相似文献   

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya     

M. A. Kahn 《洁净——土壤、空气、水》2000,28(2):95-101

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.  相似文献   

红虾(Palaemon gravier)脂肪酸分析     

张强 《海洋科学进展》1998,(1)

对红虾虾头和虾肉中的脂肪进行了提取和测定。脂肪甲酯化后,采用５０ｍ×０．３５ｍｍｉ．ｄ．ＰＥＧ－２０Ｍ玻璃毛细管柱,ＦＩＤ检测器,并结合ＧＣＬＭＳ进行了脂肪酸分析。结果表明,虾头中脂肪含量达１０．８×１０－２,其不饱和脂肪酸６８．８×１０－２,ＥＰＡ＋ＤＨＡ占２４．１×１０－２;虾肉中脂肪仅为３．９×１０－２,其不饱和脂肪酸６９．８×１０－２,ＥＰＡ＋ＤＨＡ为２７．３×１０－２。  相似文献   

科尔沁沙地奈曼旗普通风砂土中的粘土矿物     

韩广  张桂芳  李节通 《中国沙漠》1998,18(1):27-31

通过对科尔沁沙地奈曼旗普通风砂土中粘土矿物的研究,结果表明这类土壤中的粘土矿物主要是伊利石,其次为高岭石、绿泥石、伊利石-蒙脱石混层矿物;它们主要来源于母质,其次来自成土过程,降尘输入量极有限。随成土过程不断进行,粘土矿物主要遵循铝硅酸盐矿物→绿泥石→绿泥石-蒙脱石→蒙脱石顺序演变。由于母质本身贫乏、成土过程较弱以及比重差异使蒙脱石有独特的搬运与沉降行为,共同造成土壤中缺乏蒙脱石。  相似文献   

Lack of mitochondrial genetic structure in the endangered giant clam populations of Tridacna maxima (Bivalvia: Cardiidae: Tridacninae) across the Saudi Arabian coast     

Ben Othmen Abdelwahe  Abhary Mohame  Deli Temim  Ouanes Zouhour  Alhuwaiti Nour  Dimassi Najet  Mansour Lamjed 《海洋学报(英文版)》2020,39(2):28-37

The present investigation focuses on population genetic structure analysis of the endangered giant clam species Tridacna maxima across part of the Red Sea,with the main aim of assessing the influence of postulated potential barriers to gene flow(i.e.,particular oceanographic features and marked environmental heterogeneity)on genetic connectivity among populations of this poorly dispersive bivalve species.For this purpose,a total of 44 specimens of T.maxima were collected from five sampling locations along the Saudi Arabian coast and examined for genetic variability at the considerably variable mitochondrial gene cytochrome c oxidase I(COI).Our results revealed lack of population subdivision and phylogeographic structure across the surveyed geographic spectrum,suggesting that neither the short pelagic larval dispersal nor the various postulated barriers to gene flow in the Red Sea can trigger the onset of marked genetic differentiation in T.maxima.Furthermore,the discerned shallow COI haplotype genealogy(exhibiting high haplotype diversity and low nucleotide diversity),associated with recent demographic and spatial expansion events,can be considered as residual effect of a recent evolutionary history of the species in the Red Sea.  相似文献   

核电站温排水遥感定量监测方法研究     

徐进  王海霞  曲颖丽  王庆名 《地理信息世界》2019,26(1):82-86

以红沿河核电站附近海域为研究对象,基于2014年到2017年获取的Landsat-8卫星遥感影像数据,对核电站温排水空间等级分布特征监测技术进行了研究。首先,利用MCSST(McClain Sea Surface Temperature)温度信息提取模型,计算研究区海表温度(Sea Surface Temperature,SST)数据;再依据海湾平均温度法,计算出海面基准温度;其次,进行差值计算,根据温升强度等级,得到研究海域的等级分布数据;最后,基于掩膜技术与监督分类方法,剔除非核电站温排水影响的温升区,得到研究区海域温排水等级分布(Distribution of Thermal Plume,DTP)特征与统计数据,建立了一套核电站温排水遥感监测方案。实验结果表明,冬季的核电站温排水遥感定量监测结果较好,其他季节受多种因素影响,难以准确定量获取核电站的温排水影响结果。  相似文献